Machines which cut hard surfaces, such as concrete and asphalt and the like, have a rotating cutting element with a plurality of cutting tools mounted thereon. During the operation of the machine, each of the cutting elements is brought in contact with the hard surface to remove a small portion of the material and thereby advance the cut. The cutting tools for such machines are symmetrical about a longitudinal axis and have a forward cutting end into which a hardened tungsten carbide insert is fitted, and a rearward cylindrical mounting end which is retained in a mounting block of the machine. While the tools for certain machines are adapted to rotate within the mounting block, other cutting tools are non-rotatably mounted in the block. Presently, the non-rotatably mounted tools have a threaded stud at the rear end of the mounting portion thereof, and some portion of the tool has a non-circular cross section which mates with a complementary non-circular portion of the mounting block such that the tool is non-rotatably retained. When the tool is inserted into the mounting block of the machine, a lock nut is threaded to the stud to retain the stud in a cylindrical aperture extending through the mounting block. Typically, the lock nut has a radial hole extending through the wall of the nut with a plastic insert extending therethrough, and the plastic binds into the threads of the stud as the nut is tightened. As an alternative to a lock nut, some portion of the threads of the nut or stud may be damaged after a nut is assembled thereto such that the nut cannot subsequently be removed without the application of substantial torque. When lock nuts or damaged threads are used to retain the tool, the tool must be non-rotatably mounted so as to resist the large torque required to remove a nut having a plastic insert, or a nut for which the threads have been damaged.
Presently, such tools have a cylindrical mounting a portion and a tapered forward end, and some portion of the tool has a non-circular cross section, such as a flat. The mounting block, on the other hand, has a cylindrical aperture to retain the mounting portion of the tool and a forward portion has a complementarily shaped section which engages the non-circular portion of the tool.
There are certain drawbacks to the currently used methods of mounting tools into a mounting block of a cutting machine. Where the tool has a portion with a non-circular cross section, such as a flat, which engages a complementarily shaped portion of the mounting block, such as a ridge, the tool can be inserted in only a finite number of orientations. This structure increases the installation time for mounting such tools onto machines, and increase the manufacturing costs of both the tool and the mounting block.
Another problem with existing non-rotatable tools is that the anti-rotation device is typically a ridge on the forward surface of the block which engages a flat on the outer circumference of the tool. The metal from which the block and anti-rotation ridge are cast or forged, however, is relatively soft and is subject to being washed away by friction as the particles broken free by the tool are removed from the proximity of the cut. Over a period of time, the anti-rotation ridge on the block will become entirely washed away, thereby rendering the block unusable for receiving another tool.
It would be desirable, therefore, to provide for the mounting of a tool within a machine which is completely symmetrical about its longitudinal axis, but would be non-rotatable during use. Furthermore, it would be desirable to have a mounting nut which would not loosen as a result of vibration, but could be loosened and reoriented to a different angle chosen by the operator.
As an alternative to the above, it would be desirable to provide a means for preventing the anti-rotation device on the mounting block from being washed away.